Many interactions in nature are governed by volatile compounds released by, for example, plants or insects. The power of these compounds to affect the behavior of phytophagous insects, has led to a need for methods to collect and identify them. The most commonly utilized technique relies on adsorption of the volatile compounds on a polymer like SuperQ, charcoal or Tenax which then are extracted with a solvent to release the compounds. The extracts are typically analyzed by GC/MS utilizing split/splitless or on column injection. The main problems with this technique are that the extraction step dilutes the sample which makes it necessary to collect for a relatively long time, typically from 1 to 24 hours or to use more material releasing the volatile compounds. However, in a natural situation, for example, the release of leaf volatiles or insect pheromones, the volatile organic compounds might be released during a short or specific time period or the pattern of the volatiles might change over time, thus long time collections might result in a mixed sample that does not mimic a natural blend. Furthermore, increasing the source releasing the volatiles might not result in the desired increase of release. For example, the release of pheromone by a single insect might be hampered by the presence of more insects or the physical limitation of a collection enclosure limits the amount of plant material that can be contained. The technique of choice for those situations has been to use the adsorbent Tenax 16 that can be desorbed by heat in a technique suitably named Thermal desorption (FIG. 1). With this solvent free injection technique, the filter 16 containing the sample is placed in a specifically designed oven where the volatile compounds are released from the filter 16 by elevated temperature and by a constant flow of a carrier gas such as He into Gas inlet 20. The gas is passing through a trap 19, cold with liquid CO2 or sometimes liquid N2, where the volatile compounds will be retained. After a suitable desorption time the cryo trap 19 is flash heated to release/inject the trapped compounds onto the GC column 24 that is temperature programmed as with a standard solvent injection. The desorption oven 11 as well as the cryo trap 19 might be located in a separate unit outside the gas chromatograph in which case there is a substantial transfer line 14 between the cryo trap 19 and the GC or the cryo trap 19 might be located in the GC oven 11 in which case there might be a transfer line 14 between the desorption unit and the cryo trap. Whenever transfer lines 14 are used, these need to be inert and sufficiently heated to eliminate any unwanted adsorption and/or degradation. The desorption of the Tenax filter 16 creates less of a degradation problem since, for example, sesquiterpenes are totally desorbed in less than 2 minutes at a temperature of 130° C. to 150° C. and temperatures above that are rarely needed. The germacrene family of sesquiterpenes as well as the 12 carbon terpenoid pregeijerene will degrade at temperatures above 150° C. and are typically not degraded by the desorption step while those types of labile compounds rarely survive thermal desorption injection lays due to the design of cryo traps. First, cryo traps are typically evenly cooled leading to aerosol formation at the interface where warm desorption gas is abruptly cooled down to −78° C. (with CO2), or lower. The trap therefore either has to be sufficiently long to trap aerosol droplets or be filled with, for example glass wool, to increase the surface area. To inject a sample onto the column 24, these cryo traps must be flash heated to 200° C. or higher temperatures to eliminate chromatographic peak broadening. This, in combination with active sites in the traps, such as glass wool, is the major source of sample degradation often observed with thermal desorption and very much eliminates its usefulness for natural product analyses.
Thus, what is needed in the art is a new cryo trap 18 that easily adapts to existing GC/MS systems and utilizes existing splitless injectors 11 as a desorption oven to which the cryo trap 18 of the present invention can be easily attached, as will be clear from the following disclosure, the present invention provides for this and other needs.